Hi all
Im just getting started in the electronics world and am currently making a 24v battery pack. Everything is complete on the pack however im stuck on the final hurdle, and i would have thought this would have been the easiest aspect of the project!
All i want to do is add an LED so that when the pack is turned on, the LED illuminates. I understand i must have a resistor in place on the hot side before it meets the LED to drop the voltage, however after frying a few LED's already, im lost. Using an LED that has a voltage of 2.2 and a max current of 25mA, the calculator told me i need a 1W 1200 Ohm resistor. This failed. When i put it on the multimeter, i could only get a reading on the 200 ohm setting, to which it read 10.0. Having checked the colours, it would appear the shop gave me a 10 ohm resistor instead.
I do have a working example on a battery pack someone else made, the resistor looks to be GREEN BLUE RED BROWN which would make it 5.6k ohms. The picture below is it taken out and tested on the multimeter on the 20k Ohm setting.
http://s13.postimg.org/twuyicn07/20131015_182429.jpg
There is another LED which appears to have a diode also connected. I believe this LED turns off when the battery level is low. The resistor on this one appears to be RED BLACK BROWN BROWN. It measured 0.08 on the 20k setting and combined with the diode, they had a resistance of 3.38. Here is a picture
http://s13.postimg.org/k0tviph87/20131015_182355.jpg
Could anyone please explain any of this to me please. What do the reading mean that i have found on the multimeter. I am after the correct resistor to power a typical 2.5v 25mA LED. Do these resistors need to be absolutely precise?
Many thanks for any help
Im just getting started in the electronics world and am currently making a 24v battery pack. Everything is complete on the pack however im stuck on the final hurdle, and i would have thought this would have been the easiest aspect of the project!
All i want to do is add an LED so that when the pack is turned on, the LED illuminates. I understand i must have a resistor in place on the hot side before it meets the LED to drop the voltage, however after frying a few LED's already, im lost. Using an LED that has a voltage of 2.2 and a max current of 25mA, the calculator told me i need a 1W 1200 Ohm resistor. This failed. When i put it on the multimeter, i could only get a reading on the 200 ohm setting, to which it read 10.0. Having checked the colours, it would appear the shop gave me a 10 ohm resistor instead.
I do have a working example on a battery pack someone else made, the resistor looks to be GREEN BLUE RED BROWN which would make it 5.6k ohms. The picture below is it taken out and tested on the multimeter on the 20k Ohm setting.
http://s13.postimg.org/twuyicn07/20131015_182429.jpg
There is another LED which appears to have a diode also connected. I believe this LED turns off when the battery level is low. The resistor on this one appears to be RED BLACK BROWN BROWN. It measured 0.08 on the 20k setting and combined with the diode, they had a resistance of 3.38. Here is a picture
http://s13.postimg.org/k0tviph87/20131015_182355.jpg
Could anyone please explain any of this to me please. What do the reading mean that i have found on the multimeter. I am after the correct resistor to power a typical 2.5v 25mA LED. Do these resistors need to be absolutely precise?
Many thanks for any help